Simulation of residual stresses by shot peening

Shot peening is a cold working process in which small spherical parts calle d shots are blasted on a surface of a metal work-piece with velocities up t o 100 m/s. This treatment leads to an improvement of fatigue behavior due t o the developed compressive residual stresses and also to an increase of th e surface hardness due to the cold working effect of shot peening. The aim of the paper is to simulate this process with the help of the finite elemen t method in order to predict the development, magnitude and distribution of the residual stresses in accordance with the parameters, which are, e.g. s hot velocity, shot diameter and material parameters. In the first step an a xisymmetric model is used to simulate the perpendicular impact of an elasti c sphere against an elastic-plastic surface. Due to the large plastic defor mations, 9/3 mixed formulation elements are used instead of the usual nine- node displacement formulated elements, which are not well suited for this t ask. In a second step it is shown how the results of the axisymmetric appro ach can be transformed into a three-dimensional model in order to investiga te the effect of adjacent shots. (C) 1999 Elsevier Science Ltd. All rights reserved.